Preliminary Results on the Composition and Structure of Soft-Bottom Macrobenthic Communities of a Seamount: the Galicia Bank (NE Atlantic Ocean)

Abstract

The Galicia Bank (Atlantic Ocean, NW Iberian Peninsula) is a flat-topped seamount located about 200 km from the northwest coast of Spain. This bank is included in the LIFE+ “INDEMARES” project, who aims to identify priority areas of conservation in the Spanish seas. In 2010 and 2011 two oceanographic surveys were carried out to investigate species and habitats of this deep ecosystem. A total of 28 stations were sampled using a box corer with a sampling area of 0.09 m2, in order to evaluate the distribution and biodiversity of the macroinfauna of the Galicia Bank. An additional sediment sample was taken at each station to analyse the granulometric composition and the organic matter content. Sediments were mainly sandy in nature (medium, fine and very fine sands), with low levels of organic matter content. The samples analysed yielded a total of 1189 individuals, belonging to 89 families. Polychaetes were the best represented group in total number of individuals (67%), followed by molluscs (14%). Echinoderms (9.7%), crustaceans (6%), and the Others group (Nemertea and Sipuncula) (3.9%) were less abundant. Two major macrobenthic assemblages were determined through multivariate analyses. Sedimentary composition was the main factor structuring the benthic community, separating medium sand stations from those that had finer sediments.